Oil burner with air directing means



March 28, 1961 w. SANBORN OIL BURNER WITH AIR DIRECTING MEANS 2Sheets-Sheet 1 Filed Sept. 4, 1957 w QM o 1w. m ww v .M ml.

X M M March 28, 1961 w. SANBORN 6,

OIL BURNER WITH AIR DIRECTING MEANS Filed Sept. 4, 1957 2 Sheets-Shee t2 IO iii-9'7 Mornegs 2,976,920 Patented Mar. 28 1961 01L BURNER WITH AIRDIRECTING MEANS William L. Sanborn, Milwaukee, Wis., assignor to Bell &Gossett Company, a corporation of Illinois Filed Sept. 4, 1957, Ser. No.681,930

4 Claims. (Cl. 158-76) This application is a continuation-in-part of mycopending application Serial No. 588,075, filed May 29, 1956.

This invention relates to oil burners and particularly to liquidatomization oil burners of the kind used in small domestic heatingplants.

It has long been known that in large capacity oil burners of the highpressure or gun-type, the use of high oil pressures, usually in excessof 100 lbs. per square inch, enables fuel to be fed at a high rateusually in excess of two gallons per hour, and that fuel in suchinstances is atomized by what is termed liquid atomization. Largecapacity burners of the aforesaid kindhave met with wide commercialsuccess, but Whereeiforts have been to utilize similar structures insimilar oil burner installations where low or medium oil pressures areemployed, there has been very little success in obtaining acceptableoperating characteristics in small burner installations where fuelconsumption is to be from about one-half gallon to about one andone-half gallons per hour. In such small capacity burners the oilpressures employed are from about forty pounds to about seventy poundsper square inch, and burners of such low capacity, of course, representa high proportion of the oil burners that are sold and used. The majorfaults that have been experienced with such small oil burners have beentheir noisiness and inefficiency, and in my aforesaid co-pendingapplication I have disclosed an oil supply and air control means wherebythe efliciency of such burner has been greatly increased and the noise 2spect to prior oil burners, it is the primary object of the presentinvention to enable such objectionable characteristics to be overcome ina simple and effective manner, and to accomplish this in such a way asto attain unusual efiiciency of operation coupled with almost completeabsence of noise. A more specific object of the present invention is toenable low capacity oil burners to operate at greatly increased flametemperatures, with low stack temperatures, low smoke or soot production,and with a high CO reading, and related objects are to accomplish thisin such a way that natural draft is not needed and in such a way thatefliciency is maintained even where there is appreciable back pressurein the combustion space, to eliminate the necessity for the usualfirebox, and through the attainment of high flame temperatures, toenable the area of heat transfer surfaces of such heaters to besubstantially reduced.

Other and further objects of the present invention will be apparent fromthe following description and claims, and are illustrated in theaccompanying drawings, which by way of illustration, show a preferredembodiment of the present invention and the principles thereof, and whatI now consider to be the best mode in which I have contemplated applyingthese principles. Other embodiments of the invention embodying the sameor equivalent principles may be used and structural changes may be madeas desired by those skilled in the art without departing from has beenreduced. The present invention constitutes an improvement upon my priordisclosure under which there is marked simplification of the structureand improvement in operation as compared with the structure shown in myaforesaid co-pending application.

To more specifically set forth the deficiencies of prior low capacityoil burners of the aforesaid type, it may be pointed out that in almostall present day oil burners that have a fuel capacity of one gallon perhour, or less, the inefliciency is such that they rarely have a flametemperature as high as 2000 F., and they operate at a C0 reading that israrely over 7, and with stack temperatures of from 500 F. Such burnersall require fireboxes to maintain adequate flame propagation, and evenwith such fireboxes, diliicultly is experienced in maintaining a stablefire. Such small capacity burners also have required an appreciablenatural draft, usually of a high order, and this has contributed to theinefficiency of the burners. These low capacity burners also produce ahigh soot content in the flue gases so as to be dangerous and objectionable in this respect. I

The foregoing performance factors of present day small capacity oilburners have, of course, influenced and increased the size and cost ofheaters or boilers, and have resulted in undue costs ininstallation,operation and upkeep of such oil burners and the related equipment.

Having in mind that the oil burner structure disclosed in my aforesaidcopending application overcomes the basic objectionable characteristicabove set forth in rethe invention.

In the drawings:

Fig. 1 is a horizontal plan view taken through the airtube and nozzlestructure of an oil burner embodying the features of the invention.

Fig. 2 is a front view of the swirler and nozzle unit.

Fig. 3 is a rear view of the nozzle and swirler unit.

Fig. 4 is an enlarged transverse cross-sectional view of the air-swirlerand nozzle assembly. 1

Fig. 5 is a cross-sectional showing further details of the internalconstruction of the nozzle.

Fig. 6 is an enlarged view similar to Fig. 4 and showing further detailsof air and oil flow.

Fig. 7 is a fragmentary front view of the structure shown in Fig. 6; andI Fig. 8 is a schematic view illustrating symmetrical relationships ofthe components of the air and fuel supply.

The invention is herein illustrated as embodied in a nozzle-air swirlerunit 10 that forms a part of an oil burner 11, and the oil burner has anair tube 12 at the forward end thereof which projects through and beyonda wall 13 of the combustion space 14 of a heater. The nozzle-air swirlerunit 10 embodies many of the structural and operational characteristicsthat are disclosed in my aforesaid copending application, and referenceis hereby made to such application and the disclosure is herebyincorporated herein insofar as it is not inconsistent with the presentdisclosure. 7

The nozzle-air swirler unit 10 as herein shown comprises a nozzle 15upon which a swirler 16 is mounted, and the nozzle 15 is secured on theforward end of an-oil supply pipe 17 and is connected at its rear end toa pipe 18 by means of a union-type coupling 19, while the forward ornozzle end of the pipe 17 is supported and centered in the forward endof the air tube 12 by the swirler 16 which is positioned within aforward positioning cap 20 that is fixed in the forward end of the airtube.

The oil supply pipe 17 also serves as a carrier for electrical ignitionmeans comprising a spark plug 22 secured by a clamp 23 to the pipe 17and having an elecsure atomized and discharged forwardly through anaxial discharge orifice D of the nozzle to form a hollow conical spray Sof oil in the combustion space, and air isfed forwardly through the airtube 12 at a predetermined rate so that such air is intermixed with theoil spray to form a combustible mixture that may burn forwardly of thenozzle 15 as a flame F.

The present invention is concerned with the production of a stable, hightemperature, eflicient flame F and, as will be described in greaterdetail hereinafter, the

present inventionenables this flame F to be maintained in asubstantially constant size and location so that efficient andsubstantially noiseless combustion is attained.

The structural features and relationships that enable such efiicient andnoiseless combustion to be attained will be described in detailhereinafter, but as a preliminary to such specific description it may bestated that it is my present theory that these results are produced bycoordinating the air supply and fuel supply so that, with respect to theaxis of the nozzle, the air supply and the oil supply are individuallysymmetrical, and are symmetrical to each other, and by supplying flamepropagation air at the nozzle tip so that flame propagation starts closeto the tip. It is my present theory that the presence of flamepropagation air at the tip assures continuity and uniformity ofcombustion at this point, thus to eliminate pulsation of the flame Ftoward and away from the nozzle, while the symmetry of the air and fuelsupplies about and with respect to the nozzle axis, and with respect toeach other, assures uniformity or symmetry of combustion in acircumferential sense and eliminates any tendency toward lateralpulsation of the flame F. As a result of such control of the fuel andair, the combustion of the fuel is completed while the fuel is within arelatively short distance of the air tube 32 and the flame F maintains asubstantially constant position and a substantially constant form andsize.

Thus, as shown in Fig. l, the flame F has the form of a parabolic conoidthat is symmetrically positioned on the axis of the fuel nozzle 15 withthe small end of the flame disposed at substantially onequarter inchfrom the nozzle tip. In a burner of the present construction operatingat about one. gallon per hour the flame F has a length of about 4 inchesand a maximum diameter of about 4 inches, and the flame burns withoutpulsation or noise.

Under the present invention the nozzle 15, the swirler 16 and the sparkplug 22 are assembled as a unit that may be readily mounted or removedfrom the air tube 12. Thus, the assembly may be moved forwardly into theair tube 12 with the outer edge portions f the swirler 16 in engagementwith the tube 12 and finally with the end cap 21 and the outer forwardportions of the swirler 16 engage an inturned annular flange 26F of theair cap to limit and determine the forward position of the nozzle 15 andthe swirler 16. The coupling 19 which is in the nature of a union isthen attached to the pipe 18 so that the nozzle-swirler unit fit islocated in a fixed position where it is coaxial with respect to the airtube 12.

One of the important characteristics of the present structure is theprovision of a relationship between the elements which causes thoseforward surfaces of the nozzle 15 where carbon deposits would usually beformed to be kept clean and free from oil so that carbon formation onthese nozzle surfaces is prevented. In attaining this result thespecific form of the nozzle 15 is quite important as well as therelationship of the nozzle to the air directing means of the swirler l6,and as a preliminary to the description of functioning in this regard,the specific form of the nozzle will be described. Thus, the nozzle 15is in many of its characteristics of conventional construction as shownin Fig. 6 of the drawings, and the specific structural characteristicsand relationtionship that are important in attaining the objectives ofthis invention will be described in detail. As shown in Fig. 6.of thedrawings, the nozzle 15 comprises an outer forward tip 1ST in theforward end of which the axial discharge passage 15!) is formed. Therear end of the tip 1ST takes the form of a nipple 15N to which a unionfitting 17U on the forward end of the supply pipe 17 maybe connected,and just forwardly of the nipple 15N, a nut portion 15H is provided.

Within the tip 151", an inner core 150 is provided and is held in placeby a set screw 158 that is threaded axially into the rear end of thenipple ISN. The core 15C and the set screw 153 have aligned axialpassages 15? formed therein so that oil fed forwardly through the pipe17 enters these passages and is discharged radially from the core 15Cthrough bores 15A into a pressure space 15B that surrounds the core 15Cwithin the forward portion of the tip EST. The forward portion of thecore 15C is formed as a plug that closes the forward end of the passageor bore 15A and has a rounded forward face 115C that has an annular areaof engagement with a rearwardly facing internal surface 115T, and theoil from the pressure chamber, in order to reach the discharge orifice15D, passes this annular area of engagement of the surfaces 115C and115T through passages that are formed as slots 1158 in the surface 115Cof the core. The oil that thus passes through these slots 115$ enters aspace formed between the forward surface of the core 15C and the rear orinner end of the discharge passage 151) so that the streams of oil thatare formed as the oil moves through the slots 1158 may be dischargedthrough the passage 15D.

It is important to note that the slots 1158 are symmetrically related toeach other and to the axis of the nozzle, and are so positioned that theoil passing through these slots is given a swirling motion about andwith respect to the axis of the nozzle, and this relationship is knownin the art and is shown in Fig. 5 of the drawings. The manner in whichthe streams of oil pass into the discharge orifice 15D and aredischarged as a spray S will be discussed in some detail hereinafter.

On the forward face of the nozzle tip 1ST a novel and extremelyimportant form or shape is employed which functions as will hereinafterbe described in cooperation with the swirler '15 to assure that oil doesnot flow rearwardlyalong the nozzle surface. Thus, as shown particularlyin Figs. 4 and 6 of the drawings, the forward face of .the nozzle tip151 is formed with a forwardly converging conical surface 315C thatextends to a point where it is of relatively small diameter, and at thispoint the conical surface 315() merges with or meets a cylindricalsurface .4156 that extends forwardly in a concen tric relation withrespect to the nozzle axis to meet a forward nozzle face 15F that iscircular in form and through which the discharge orifice 15D opens.

The fuel oil that is being fed under pressure through the nozzle 15 hasa swirling motion imparted thereto by reason of the angular positioningof the slots 1-153, and it is formed into four distinct and relativelyfine streams of oil that leave the respective slots 1158 and move with aspiral or swirling motion through the outlet or dis charge opening 151).As this fuel leaves the discharge opening 15D it forms into a hollowconical spray S that may be described in general as constituting a thinlayer of finely divided oil particles shaped in the form of a cone thatis centered on the axis of the nozzle 15 and has its apex locatedapproximately at the forward end of the orifice 15D. The internal angleof the cone that constitutes the spray S varies according to knownpractices in accordance with the specific internal design of the nozzle15, and the nozzle herein shown is one that produces what is called aspray as indicated in Fig. 6, but under the present invention ditferentspray angles may be used as, for example, a 60 or 75 spray angle, as iscommon in the art.

1 As above pointed out, the spray S is made up in a general sense as athin layer of oil that defines a cone,

but I haveobserved, and in accordance with the present invention, havemade advantageous use of the fact that within or as a part of this thinlayer there are well defined concentrations of fuel that take the formof streams SS.

as indicated on an exaggerated scale in Fig. 8. These streams SScorrespond in number and in circumferentiallocation with the number andlocation of the slots 1158, and between the streams SS, the spray isdefined by the thin layer S as indicated in Fig. 8. As will becomeapparent from the following description, the supply of air to thecombustion space is controlled by the swirler 16 and the design of theswirler is correlated with the form of the spray, as above described, sothat the proportioning of the air and fuel is maintained uniformthroughout the entire circumference of the spray, and through thiscontrol, the present invention eliminates the usual tendency of theflame to burn unevenly in a lateral sense. This'results in theattainment of what may be termed lateral stability of the flame, as willbe described hereinafter.

The swirler 16 embodies certain of the physical characteristics of theswirler shown in my prior Patent No. 2,485,244, as well as certain ofthe physical characteristics of the swirler of my aforesaid copendingapplication, but as will become apparent hereinafter, the swirler '16,as compared with the structure of such patent, includes additionalcooperating structural elements and accomplishes additional functionsthat enable the desired efficiency and operating characteristics to beattained in small oil burners.

' Thus the swirler 16 constitutes a singleblade unit having a pluralityof segmental blades B formed integrally with and as outward generallyradial extensions of a coneshaped inner air directing member C. Theswirler 16 is formed from sheet metal as by stamping and formingoperations in which the several blades B are defined by cutting a seriesof radial slits 30 which at their inner ends have circumferentiallyextending slits 31 formed at a uniform distance from the center of thecone C and extended in the same circumferential direction from therelated radial slits 30. After the slits 30 and 31 have been formed,metal of each segment is bent forwardly to give the desired fan-likeshape to the several blades B. The several blades B are of identicalform and are uniformly spaced. As will be evident in Fig. 7 of thedrawings, this fan-like formation enables the blades B to impart changesof direction to the forwardly moving air that must pass from the airtube 12 through the swirler 16. Thus air will be directed inwardly in aradial direction through the opened slit 31 to provide an inwardlydirected air component 32 at each of the several blades B, and also airwill be directed with a swirling component gem each of the severalblades B as indicated at 33 in The inwardly directed stretms orcompontnts 32 of air are directed somewhat forwardly along the forwardsurface of the air directing cone C as will be evident in Fig. 6 of thedrawings.

At their outer forward corners, the several blades B are interconnectedby an annular connecting band 34 that is made of sheet metal and iswelded or brazed to the corners of the several blades B as indicated at34W in Fig. 6.

The swirler 16, as above pointed out, is supported in a fixed andcentered relationship on the nozzle 15, and this is accomplished by asupporting spider that is made from sheet metal and has an annularmounting rim 35R of angular cross-section which fits with a snug pressfit on the annular surface of the tip 1ST just forwardly of the nutportion 15H, and the mounting rim 35R has a plurality of connecting arms35A that are relatively narrow, as will be evident in Fig. 3 of thedrawings, and which extend outwardly and then forwardly for weldedconnection as at 35W with the outer rear surface of the air-directingcone C. The narrow arms 35A provide for adequate area through whichforwardly,

moving air may move to strike the outer rear face. of the air-directingcone C so that such air may be directed inwardly and forwardly along theconical surface 315C of the nozzle tip 1ST for subsequent dischargethrough the central discharge opening 37 of the air-directing cone C.The discharge opening 37 is, of course, concentric with the axis of thenozzle and is spaced outwardly from the cylindrical surface 415C of thenozzle tip. As shown herein, the opening 37 is disposed in a plane thatis relatively close to the rear end of the cylindrical surface 415C, butthis relationship may be varied to a considerable extent within thepurview of this invention.

The conical forward surface 315C of the nozzle tip and the rear face ofthe air-directing cone C are arranged so as to converge slightly towardeach other as they approach the axis of the nozzle, and thisrelationship is important in that it imparts an increased velocity tothe air that is moving therethrough toward the discharge opening 37.

The inwardly moving cone of air that passes between the cone C and thesurface 315C has been indicated diagrammatically at 38 in Figs. 6, 7 and8, and when this air reaches the discharge opening 37 its direction ofmovement is altered in a large measure by the cylindrical surface 415Cof the nozzle tip so that this air is discharged in a forward directionas a sleeve 39 of air that moves longitudinally along the cylindricalsurface 415C. The forwardly moving sleeve 39 of air thus moves forwardlypast the annular corner where the cylindrical surface 415C meets theface 15D so that the sleeve of air strikes the spray S in a uniform andsymmetrical manner relatively close to the point where the spray Semerges from the nozzle. The forwardly moving sleeve of air that hasbeen identified at 39, and which thus strikes the spray S, is importantin further breaking up or atomizing of the oil of the spray and inmixing with the spray to assure a combustible mixture closely adjacentto the nozzle tip, and it is also of particular importance in that itactsin a novel manner to assure thatoil from the forward tip face 15Fcannot move in a rearward direction along the forward faces 415C and315C of the nozzle. Thus, it may be noted that the face 15F of thenozzle tip operates in a wet condition in that oil that is notdischarged as a part of the spray S gathers in small amounts on theforward face 15F. This wet tip-face condition has long been known andrecognized in the oil burner art, and it has been known that it is thisoil on the. wet tip-face of the nozzle that hts been responsible forcarbon deposits or varnishing on the nozzle surface. I have found thatwhere rapidly moving air is discharged as a sleeve past andperpendicular to the outer annular corner of the nozzle tip face 15F,any oil that has moved outwardly or radially to the annular edge of thisface is picked up by advancing sleeve of air and is thus transportedforwardly into the spray so that it is burned in the normal manner. Whenthis arrangement is employed, it has been found that no carbon depositsare formed on any of the for ward surfaces of the nozzle.

The inwardly directed air indicated at 32 as flowing inwardly from therespective blades 16 and along the forward surface of the cone C is ofcourse consolidated with the sleeve 39 of air adjacent the apex of thespray S, and this is accomplished in such a way that symmetry of airsupply is maintained and further break up and early combustion of thefuel is assured.

With the swirler 16 related to the nozzle 15 as above described, thedesired flame propagation air is supplied relatively close to the nozzle15, and by using a structure that provides such flame propagation air inrelatively large volume, it is found that the fuel starts to burn almostimmediately after it is discharged from the nozzle 15, thus to locatethe flame F, quite close to the end of the nozzle. The air that emergesfrom the swirler, as at 33, has a swirling motion and engages thesprayed fuel so as to provide additional air for combustion while at thesame time acting to confine the flame Within the envelope afiorded bythe advancing swirling body of air.

An important characteristic of the present invention is that the air issupplied to the fuel in a symmetrical relationship with respect to thefuel spray, and in this respect the specific composition or form of thespray, as hereinabove described, is important. Thus, I have found thatWhere four slots 115$ are used in a nozzle, the flame characteristicsare vastly improved by utilizing a swirler construction in which thenumber of blades is equal to the number of slots employed in the nozzlemultiplied by a Whole number. In the present instance, where four slots1153 are used in the nozzle, the desired combustion characteristics areattained by using eight blades B in the swirler. The swirler, however,may, under the present invention, be formed for use with a four-slotnozzle so as to have an even greater number of blades, such as twelveblades each, or sixteen blades. This same general theory may be appliedto other nozzles having different numbers of slots 1158. Through thisarrangement and relationship, the air supply is symmetrical in acircumferential sense to the streams SS of the spray as Well as to theintermediate web-like portions of the spray, and in Fig. 8 of thedrawings this symmetrical relationship has been schematicallyillustrated.

In considering the symmetry of the air supply and the oil supply withrespect to each other and with respect to the nozzle axis, it isimportant to note that, in attaining the desired swirling movements andinward movements of the air, the blades B of the swirler act initiallyto divide the main air stream into a plurality of separate air streamswhich have been schematically indicated by arrows in Fig. 8, and furtherthat the nozzle 15 produces a spray that includes a conical web-likeportion with a number of discernible streams SS therein corresponding tothe number of nozzle slots 1158. Thus, in carrying out the basic conceptof the present invention, each stream SS (along with the related thinweb portions of the spray) is acted upon in a like manner by one ofseveral like groups of related air streams, with the result that eachportion of the spray is subjected to like forces and is supplied withlike amounts of air.

To consider the foregoing analysis more specifically as applied to theillustrated embodiment, each blade B may be considered as producing orcausing a circumferentially directed air stream 33 that passes throughthe related slot 30 and an inwardly directed air stream 32 that passesthrough the related slot 31, such inward air streams 32 beingsubstantially directed slightly forwardly by the outer surface of thecone C.

InFig. 8 of the several streams of air that are produced by the eightblades B are shown in relation to the spray S and its four streams SSthat are produced by a four-- slot fuel nozzle. Thus with thisparticular relationship of the number of blades B, and nozzle slots115$, and with the slots and the blades in a symmetrical orequidistantly spaced relation about the nozzle axis, each of the foursimilar segments of the fuel spray is acted upon in a similar manner bythe same number and type of air streams. This result follows regardlessof the rotativc or angular positioning of the swirler with respect tothe slots 1258 of the nozzle, and the four similar segments of the fuelspray are thus subjected to like controlling conditions and to likecombustion conditions so that lateral unbalance and lateral pulsation ofthe flame F are prevented.

With the nozzle and the swirler formed and related as thus described,the flame F maintains a steady form and position so that the fire issubstantially free from objectionable noise and is highly efficient inall respects. In

actual use it has been found that in a small capacity heater the fuelfeed rate, and the air supply rate, may be adjustably varied ormodulated over a substantial range while maintaining the eflicient andnoiseless opera tion of the burner. In such operation, the inward flowof air over the conical surface of the nozzle tip serves to keep thenozzle cool, and as this cone of advancing air passes forwardly throughthe annular opening 37 and is formed into a sleeve of air along thecylindrical surface 415C, it passes the annular outer corner of the tipface 15F and picks up any excess oil at the edge of the face 15F so asto carry the same into the flame F. The longitudinal stability of theflame F avoids contact of the flame with the nozzle and eliminatesbaking or clogging of the nozzle.

The flame propagation air that flows through the annular opening 37 soas to cool and clean the nozzle is of course intermixed with the fuel atsubstantially the apex of the fuel spray so the combustion starts and isuniformly maintained at but a short distance from the nozzle, and as aresult the burning of the fuel is completed within a relatively shorttravel of the fuel and while the fuel is well within the controllingrange of the swirling envelope of combustion air that advances betweenthe blades of the swirler.

With a small capacity burner of the construction described, operating ata fuel consumption rate of one gallon per hour of No. l or No. 2 oil, ithas been found that flame temperatures of as high as 2700 F., stacktemperatures of as low as 250 F., may be readily and consistentlyattained with CO readings of 12 and 13% and with CO readings of zero.Such performance has been attained without natural draft and even in thepresence of appreciable back pressure, and in every instance the firehas been free from noise and the flame stable in a longitudinal as wellas a lateral sense.

The low nozzle temperature that is attained by the present invention isof particular value inthat it avoids production of a clogged orvarnished nozzle so that the nozzle operates in a cool and cleancondition despite its proximity to the unusually hot flame that isproduced. Hence one of the most frequent causes of burner failure hasbeen overcome. This results in part from the longitudinal flamestability which prevents contact of the flame with the nozzle, in partfrom the continuous and symmetrical supply of flame propagation air atthe nozzle tip so that positive pressure at this point prevents rearwardflow of heated gases past the nozzle, and from the continuous flow ofcooling air over the nozzle and the swirler blades which are located inthe airstream and act as cooling fins for the nozzle.

Thus, the present invention enables a medium pressure,

liquid atomization burner to operate with extremely high efliciency andin a trouble-free manner, and since the high oil pressures, that haveheretofore been considered necessary for efficiency, have beeneliminated, the characteristic oil burner roar has been substantiallyeliminated.

From the foregoing description it will be apparent that the presentinvention enables small capacity, medium pressure, oil burners tooperate without objectionable noise and at uniform and extremely highlevels of chiciency; and further, that the stability and efliciency thusattained simplifies and reduces the cost of production, installation,operation and upkeep of small capacity oil fired heaters.

Thus while I have illustrated and described the invention in aparticular embodiment, it will be recognized that changes and variationsmay be made within the spirit and scope of the invention.

1 claim:

.1. In an oil supply and air control unit for use in a liquidatomization type oil burner having an air tube through which lowpressure air is directed in a forward direction toward an open forwardend of the tube, an oil supply pipe adapted to be mounted in the tubethrough which oil may be forced at a predetermined pressure, a liquidatomization nozzle connected to said pipe at the forward end of an airtube for receiving oil under pressure from the pipe, said nozzleincluding an outer nozzle tip having an axial discharge orifice forspraying oil forwardly from said nozzle and having an outer forward faceformed as a concentric, truncated conical surface from the smallerforward end of which a small cylindrical projection extends andterminates in a flat tip face normal to and through which said dischargeorifice opens, a cone-shape air directing member disposed forwardly ofsaid conical face and extended radially outwardly beyond said nozzle todirect air inwardly along said conical face for discharge as a forwardlymoving sleeve along said cylindrical projection and past the edge ofsaid tip face at right angles to said tip face to carry any oil presentat the edge of the tip face directly forwardly into the oil spray, amounting spider supporting said air directing member on said nozzle, anannular series of radially disposed air directing blades formed asoutward extensions of said cone-like air directing member and arrangedin uniformly spaced relation in a circumferential sense for directingair with a swirling action direction against the divergingly sprayedoil.

2. In a nozzle-swirler unit for use in a liquid atomization type oilburner having an air tube through which low pressure air is directed ina forward direction toward an open forward end of the tube, an oilsupply pipe adapted to be mounted in the tube through which oil may beforced at a predetermined pressure, a liquid atomization nozzleconnected to said pipe at the forward end of an air tube for receivingoil under pressure. from the pipe, said nozzle including an outer nozzletip having an axial discharge orifice from which a spray of oil may bedischarged in a forward direction and having an outer forward faceformed as a truncated conical surface concentric with said orifice andfrom the smaller forward end of which a small cylindrical projectionextends and terminates in a flat tip face normal to and through whichsaid discharge orifice opens, a swirler stationarily mountedconcentrically on said nozzle and having an annular series of radiallydisposed air directing blades arranged in uniformly spaced relation in acircumferential sense for directing air with a swirling action againstthe sprayed oil, and a cone-shape air directing member disposedforwardly of said conical face to direct air inwardly along said conicalface for discharge as a forwardly moving sleeve along said cylindricalprojection and past the edge of said tip face at right angles to saidtip face to carry any oil present at the-edge of the tip face directlyforwardly into the oil spray.

3. In an oil supply and air control unit for use in a liquid atomizationtype oil burner having an air tube through which low pressure air isdirected in a forward direction toward an open forward end of the tube,an oil supply pipe adapted to be mounted in the tube through which oilmay be forced at a predetermined pressure, a liquid atomization nozzleconnected to said pipe at the forward end of an air tube for receivingoil under pressure from the pipe, said nozzle including a nozzle tiphaving an axial discharge orifice and an outer forward face formed as aconcentric, truncated conical surface from the smaller forward end ofwhich a small cylindrical projection extends and terminates in a fiattip face normal to and through which said discharge orifice opens, meansforming part of said nozzle and located within said tip for formingforwardly moving oil into a predetermined number of fine streams ofequal size and pressure for discharge with a swirling action in apredetermined rotative direction and in uniformly diverging relation andin uniformly spaced relation to a circumferential sense, a swirlerstationarily mounted on said nozzle and having an annular series ofradially disposed air directing blades provided in a number that is awhole number multiple of said predetermined number of streams of oilarranged in uniformly spaced relation in a circumferential sense fordirecting air with a swirling action in said predetermined directionagainst the divergingly sprayed oil, and a cone-shape air directingmember disposed forwardly of said conical face to direct air inwardlyalong said conical face of the nozzle for discharge as a forwardlymoving sleeve along said cylindrical projection and past the edge ofsaid tip face at right angles to said tip face to carry any oil presentat the edge of the tip face directly forwardly into the oil spray.

4. In an oil supply and air control unit for use in a liquid atomizationtype oil burner having an air tube through which low pressure air isdirected in a forward direction toward an open forward end of the tube,an oil supply pipe adapted to be mounted in the tube through which oilmay be forced at a predetermined pressure, a liquid atomization nozzleconnected to said pipe at the forwardend of an air tube for receivingoil under pressure from the pipe, said nozzle including a nozzle tiphaving an axial discharge orifice and an outer forward face formed as aconcentric, truncated conical surface from the smaller forward end ofwhich a small cylindrical projection extends and terminates in a flattip face normal to and through which said discharge orifice opens, meansforming part of said nozzle and located within said tip for formingforwardly moving oil into a predetermined number of fine streams ofequal size and pressure for discharge with a swirling action in apredetermined rotative direction and in uniformly diverging relation andin uniformly spaced relation to a circumferential sense, a swirlerstationarily mounted on said nozzle and having an annular series ofradially disposed air directing blades provided in a number that is awhole number multiple of said predetermined number of streams of oilarranged in uniformly spaced relation in a circumferential sense fordirecting air with a swirling action in said predetermined directionagainst the divergingly sprayed oil, each of said blades also beingformed to direct air inwardly toward the axis of the discharge orifice,and air directing means disposed forward- 1y of said conical face todirect air inwardly along said conical face of the nozzle for dischargeas a forwardly moving sleeve along said cylindrical projection and pastthe edge of said tip face at right angles to said tip face to carry anyoil present at the edge of the tip face directly forwardly into the oilspray.

References Cited in the file of this patent UNITED STATES PATENTS1,536,046 Anthony May 5, 1925 2,120,387 Bargeboer June 14, 19382,156,405 Smoot May 2, 1939 2,221,519 Jones Nov. 12, 1940 2,267,451Eweryd Dec. 23, 1941 2,485,244 Sanborn Oct. 18, 1949 2,501,414Schoenwetter Mar. 21, 1950 2,551,276 McMahan May 1, 1951 2,603,279 PohleJuly 15, 1952 2,634,806 Hirtz Apr. 14, 1953 2,765,028 Kienle Oct. 2,1956 FOREIGN PATENTS 146,708 Sweden Aug. 31, 1954

